1. Field of the Invention
The present invention is related to a space based system for conversion of solar energy to electrical energy to be transmitted to earth stations by microwave beams.
2. Description of the Related Art
Mankind on earth is faced by two enormous and related problems. One is the rapid decline of oil reserves hastened by the increased demand for the oil itself. The other is global warming caused by the burning of oil and other fossil fuels. Solutions offered may solve one or the other but not both. Biomass is renewable but depends on combustion which exacerbates global warming. Wind turbines and terrestrial solar panels eliminate combustion but are limited to locations that are not necessarily near those in great energy need. Solar panels require a great deal of expensive real estate to serve areas of high population density. Wind turbines create “visual” pollution.
Receiving and converting solar energy in space and transmitting it to earth appears to be an innovative and exotic way of obtaining energy. However, calculating the energy to be thus received involves variables such as the size and number of satellites used. The amount of energy available from the sun must first be calculated. The following calculations illustrate this:
(a) Solar energy incident on one square meter of earth is 1000 watts. Current technology for solar panel construction permits conversion of this level of solar energy to 200 watts of electrical energy.
(b) In space, because of the lack of atmosphere, 1350 watts is incident on one square meter. This may be converted to 270 watts of electricity.
(c) The solar energy headed for the earth is the energy falling in a plane projection of the earth. Assuming an earth radius of 4000 miles, with 1609 meters/mile, the radius of the projection is 6.436×106 meters. The area of the projected disk is πr2=3.14×(6.456)2×1012=1.301×1014 m2.
(d) FIG. 2 shows the earth 60 as it moves one quarter of its yearly revolution about the sun 1, with a near polar satellite orbit which produces 75% average sunlight exposure for the satellite. Combining this arrangement with the assumption of (b) above; the calculation of (c) above and an interception rate of 0.1% of the solar energy directed toward earth yields a power calculation of 1.301×1014×0.75×270×10−3=263.5×1011=26.4×1012 watts=26.4 million megawatts. In comparison, Hoover Dam has a capacity of 1500 megawatts. Solar power calculated above is the equivalent of 26.4×106/1.5×103=17.6×103 or 17,600 Hoover Dams.
While there is no working energy satellite system currently in operation, there are many concepts of such systems. One such prior art system uses transmission from satellite antennas to ground antennas, resulting in an intermittent flow of energy. A geosynchronous satellite would provide continuous energy for 12 hours/day but its great distance from earth (23,5000 miles) would result in significant energy spread upon transmission to earth.
Orbits of satellites in various prior art systems are usually equatorial. This places the satellites over the Pacific, Atlantic and Indian Oceans and over northern South America and Central Africa. These are not areas of great energy usage, and an equatorial system is by definition limited to a single orbital plane. Typical microwave frequencies used in current concepts are approximately 2 GHz.